The last line, with the trackSingleUnit function, is highlighted and the error in Dev-C++ is:
13 C:\Documents and Settings\manjun\My Documents\c++\opengl\VisualRenderer.h expected `,' or `...' before '&' token
and
13 C:\Documents and Settings\manjun\My Documents\c++\opengl\VisualRenderer.h ISO C++ forbids declaration of `Unit' with no type